Black carbon deposited in Hariqin Glacier of the Central Tibetan Plateau record changes in the emission from Eurasia

Identifying the natural and agricultural impacts on the glaciochemistry of the Aru ice core on the northwestern Tibetan Plateau

Glaciochemical data sourced from ice cores in polar regions and the Alps have been extensively examined. However, quantitative studies on glaciochemical records of the Tibetan Plateau (TP) are scarce. To address this, we investigated annual variations in the major soluble ions (Ca2+, Mg2+, Na+, K+, NH4+, Cl-, NO3-, and SO42-) in the Aru ice core on the northwestern TP from 1850 to 2016. Applying a positive matrix factorization model, the sources of the major soluble ions and three factors to evaluate natural and agricultural impacts were identified. Factor 1, crustal dust with high loadings of Mg2+ (81.9 %) and Ca2+ (68.7 %), significantly positively correlated with wind speed and significantly negatively correlated with δ18O and net accumulation recorded by the ice core, suggesting that strong winds contributed to crustal dust transport from arid and semi-arid regions of Central Asia and deposition in the Aru glacier. However, relatively warm and wet climate prevented the transport of crustal dust. Factor 2 comprised salt lakes with high dominant loadings of Na+ (75.3 %), SO42- (64.1 %), Cl- (60.8 %), NO3- (52.2 %), and K+ (49.4 %). Declining lake water levels exposed salt lake minerals, which were carried to glaciers under the dynamic conditions of strong winds, whereas warming resulted in an expansion of glacial meltwater and lake water volume, which decreased the contribution of salt lake sediments. Therefore, the contribution of salt lake deposition decreased. Factor 3 was agricultural sources with a high loading of NH4+ (82 %), whose trend aligned closely with the population number and N productions from agricultural sources in South and Central Asia, suggesting that NH3 emissions from agricultural practices are a critical contributor to Factor 3. This study quantified the proportional contribution of natural and agricultural sources to glaciochemical composition, advancing our understanding of glaciochemical records in ice cores from source recognition to quantification.

Revised historical Northern Hemisphere black carbon emissions based on inverse modeling of ice core records

Black carbon emitted by incomplete combustion of fossil fuels and biomass has a net warming effect in the atmosphere and reduces the albedo when deposited on ice and snow; accurate knowledge of past emissions is essential to quantify and model associated global climate forcing. Although bottom-up inventories provide historical Black Carbon emission estimates that are widely used in Earth System Models, they are poorly constrained by observations prior to the late 20th century. Here we use an objective inversion technique based on detailed atmospheric transport and deposition modeling to reconstruct 1850 to 2000 emissions from thirteen Northern Hemisphere ice-core records. We find substantial discrepancies between reconstructed Black Carbon emissions and existing bottom-up inventories which do not fully capture the complex spatial-temporal emission patterns. Our findings imply changes to existing historical Black Carbon radiative forcing estimates are necessary, with potential implications for observation-constrained climate sensitivity.

Sedimentary records of human activities in China over the past two millennia and implications for the Anthropocene: A review

Human activities have profoundly transformed the natural environment and the Earth system, leading to the concept of the Anthropocene. This paper summarizes the effects of human activities on the environment in China as recorded in sedimentary archives. China is divided into core and marginal areas based on their natural and societal conditions, and changes in selected proxies for four stages since 2.0 ka are assessed. From 2.0 to 1.0 ka, tree pollen ratios, magnetic susceptibility values, stable organic carbon isotope ratios, and lead concentrations began to deviate from natural baseline (4.0-2.0 ka) values in the core area at different times depending on location. From 1.0 ka to 1950 CE, anthropogenic perturbations recorded by these proxies increased and exhibited regional changes in the core area. From 1950 to1980 CE, total organic carbon contents, stable organic carbon isotope ratios, total nitrogen contents, and stable nitrogen isotope ratios changed significantly in both the core and marginal areas. After 1980 CE, lead concentrations, black carbon and polycyclic aromatic hydrocarbons contents increased rapidly. In the latter two stages, the amounts and chronologies of artificial radionuclides and novel materials in the strata reflect their history of outputs or emissions. The boundaries for each stage correspond with important historical events. At 1.0 ka, the political center of China moved eastward, and a transportation network was established in the core area. In ca. 1950 CE, the People's Republic of China was established and the Global Acceleration began, while 1980 CE corresponds with the Reform and Opening-up of China that led to an accelerated industrialization. Our review shows that transportation networks and industries were key factors for intensification of human activities that caused Earth system to enter the Anthropocene.

Westerly drives long-distance transport of radionuclides from nuclear events to glaciers in the Third Pole

Major nuclear bomb tests and nuclear power plant incidents release large amounts of radionuclides. This study investigates beta (β) activities of radionuclides from four ice cores in the Third Pole (TP) to understand the transport routes and related atmospheric processes affecting the radionuclides deposition in glaciers of the region. All the ice cores show three major β activity peaks in the ice layers corresponding to 1963, 1986, and 2011. The β activity peak in the 1963 ice layer is referred to as the well-known 1962 Nuclear Bomb Test. Beta activity peaks in 1986 and 2011 ice layers from the Chernobyl and Fukushima Nuclear Incidents (CNI, FNI). Hysplit forward and backward trajectory analyses suggest that the radionuclides were transported by the westerly into the stratosphere and then to the high elevation TP glaciers. In the FNI case, the radionuclides traveled over Japan, the Pacific Ocean, Europe, and central Asia before being deposited in the TP glaciers. Investigations of the atmospheric circulation confirm that the stronger northern branch of westerly is responsible for high radionuclides during the FNI in the TP. Less precipitation with water vapor flux component divergence after the FNI also contributed to the enriched radionuclides.